The present invention relates to spectacle frames of the wrap-around or shield type, in particular frames adapted to receive optical lens of unconventional shape, and to optical lens elements for mounting in frames.
It is known in the prior art to manufacture non-corrective eyeglasses such as sunglasses or protective eyeglasses having wrap-around segments designed to shield the eye from incident light, wind, and foreign objects in the temporal vision field of the wearer.
Visible light and light in the UV region may enter the eye from angles as high as 100xc2x0 from the line of sight.
It has not been possible, however, in prior art sunglasses or protective eyeglasses, to provide such spectacles with significant refractive power, whilst maintaining a cosmetically acceptable appearance. The radius of curvature required to provide an ophthalmic lens including a prescription surface is such that the spectacles would produce a bug-eyed appearance, which would be cosmetically unacceptable.
Further, in International Patent Application PCT/AU97/00188 xe2x80x9cImproved Single Vision Lensesxe2x80x9d, Applicants disclose an optical lens element including a front and back surface, at least one surface being continuous, and forming a prescription (Rx) zone and a peripheral temporal zone for providing a shield in the area of the temples, which zones are smoothly blended to avoid a prismatic jump from the Rx zone to the temporal zone.
In International Patent Application. PCT/AU98/00274 xe2x80x9cLenses and Spectacles Bearing Lensesxe2x80x9d, to Applicants, the entire disclosure of which is incorporated herein by reference, Applicants disclose an ophthalmic article including an optical lens element including a front and back surface, at least one surface being continuous, and forming a prescription (Rx) zone and optionally a non-prescription peripheral temporal zone, at least one surface exhibiting a change of base curve across the field of vision of the wearer; the front and/or back surface bearing a surface correction to at least partially adjust for optical errors.
Whilst such lenses are a significant improvement, it is necessary to provide spectacle frames which will receive such unusually shaped lenses.
It is accordingly an object of the present invention to overcome, or at least alleviate, one or more of the difficulties and deficiencies related to the prior art.
Accordingly, in a first aspect of the present invention there is provided a spectacle frame shaped to receive and retain an optical lens element of the wrap-around or shield type wherein the aperture of the lens outline or edge of at least one surface of the optical lens element is of generally ovaline shape and is located on the surface a sphere whose radius of curvature corresponds to 11 Dioptre (D) or above, a toroid where the horizontal radius or curvature corresponds to 11 D or above, or a surface where the radius of curvature changes across at least one section of the lens aperture.
Such frames differ significantly in curvature from frames known in the prior art.
By the term xe2x80x9can optical lens element of the wrap-around or shield typexe2x80x9d, we mean that at least one surface of the optical lens falls on a topographical surface that wraps around the human visual apparatus or forms a facial shield.
Preferably the radius of curvature corresponds to 12 D or above, more preferably at least 16 D, most preferably at least 20 D.
The optical lens element may be removably or permanently attached to the frame.
In a preferred form the spectacle frame is itself attached to a sunglass having zero refractive power.
The optical lens element may bear a prescription surface of minus or plus power or may be piano and is preferably suitable for industrial safety or contact sport applications.
The spectacle frame according to this aspect of the present invention may be of any suitable type. The spectacle frame may permit adjustment of the inter-pupillary distance for example via attachment of a lens to the frame supports. Frames of the rimless and temple bar type may be used.
In a preferred form, the front surface of the optical lens element exhibits a change of base curve across the field of vision of the wearer, the base curves being smoothly blended to avoid a prismatic jump in the Rx zone.
By the term xe2x80x9clens elementxe2x80x9d as used herein, we mean an optical or ophthalmic lens, semi-finished lens, or lens wafer which may be utilised in the formation of an ophthalmic product.
By the term xe2x80x9coptical lens elementxe2x80x9d as used herein, we mean an optical or ophthalmic lens, semi-finished lens or lens formed from a pair of lens wafers which may be utilised in the formation of an optical lens product.
In a preferred embodiment of the present invention, at least one surface of the optical lens element is located on the surface of a toroid where the horizontal radius of curvature corresponds to 11 D or above and the vertical radius of curvature is at least 3 D less than the horizontal curvature.
In a further preferred embodiment where the lens aperture outline falls on a surface, and the radius of curvature changes across a section of the lens aperture, the change in curvature corresponds to 3 D or more. Preferably the change in curvature extends across the entire lens aperture.
In a still further preferred embodiment of the present invention, there is provided a spectacle frame shaped to receive and retain an optical lens element of the wrap-around type wherein the aperture of the lens outline or edge of at least one surface of the optical lens element is of generally ovaline shape and is located on a surface whose radius of curvature varies across the vertical or horizontal sections of the aperture of the lens outline, or both the vertical and horizontal sections thereof.
The change may for example correspond to 3 D or more horizontally and 2 D or more vertically.
The changes in curvature may be distributed smoothly across the aperture of the lens outline. The changes in curvature for example, may occur across the field of direct (forward) vision of a wearer, that is within 55xc2x0 of the line of sight for distance vision. Alternatively, the change in curvature may occur across the line of sight and within the cone of foveal vision; that is, approximately 25xc2x0 either side of the line of sight.
In a further alternative, the change of curvature may occur in the off-axis field of binocular vision, that is approximately 25xc2x0 to 55xc2x0 either side of the line of sight of the wearer. Still further the change in curvature may occur in the off-axis peripheral field, that is more than 55xc2x0 away from the line of sight of the wearer.
The changes in curvature may be viewed as asymmetric with respect to the line of sight. For example the curvature may increase in the temporal direction horizontally from nasal limit toward the peripheral viewing field or increase in down gaze vertically from the eye brows to the limits set by nose and cheek intrusion into the visual field. Alternatively the vertical and/or horizontal curvatures remain constant from the line of sight to the visual limits corresponding to brow or nasal intrusion on the visual field. The vertical and/or horizontal curvatures may remain constant from the nasal or brow limits to approximately 25xc2x0 temporal or down-gaze from the line of sight. For example the temporal curvature is constant to approximately 55xc2x0 from the line of sight.
In a further preferred aspect, the change in curvature across the aperture of the lens outline is 6 D or more in lens power equivalent, preferably 9 D or more, more preferably 12 D or more.
In a preferred aspect of the present invention, there is provided a spectacle frame shaped to receive and retain an optical lens element of the wrap-around or shield type wherein the aperture of the lens outline or edge of at least one surface of the optical lens element is of generally ovaline shape and remains substantially constant irrespective of lens power.
The spectacle frame may further include a removable or adjustable bridge or nosepiece that accommodates a wearer""s interpupillary distance and nasal structure.
In a still further aspect, the present invention provides a spectacle frame shaped to receive and retain an optical lens element of the wrap-around or shield type wherein the aperture of the lens outline or edge of at least one surface of the optical lens element is of generally ovaline shape and exhibits an increased sagittal depth of 10 mm horizontally and/or 5 mm vertically.
The curvature of the frames is accentuated for example relative to known conic or spherical frame designs without tilt.
The spectacle frame may be shaped to receive and retain an optical lens element of the wrap-around or shield type wherein the aperture of the lens outline or edge of at least one surface of the optical lens element is of generally ovaline shape and exhibits a change in sagittal depth across at least a section of the lens aperture of approximately 10 mm horizontally and/or approximately 5 mm vertically.
The change in curvature across the lens aperture is accentuated for example relative to a known conic frame of average curvature.
In a still further aspect of the present invention there is provided a spectacle frame of the wrap-around or shield type, the spectacle frame being shaped to receive and retain an optical lens element including
a front and back surface, at least one surface exhibiting a change of base curve cross the field of vision of the wearer.
The optical lens element utilised according to this aspect of the present invention may be mounted directly in a spectacle frame, for example of the wrap around or shield type. When mounted, the optical lens element may be rotated temporally about a vertical axis through the optical centre thereof (xe2x80x9ctiltxe2x80x9d), or translated so that the line of sight remains parallel to the optical axis of the lens (xe2x80x9coffsetxe2x80x9d), or a combination of both tilt and offset as described below.
In a preferred aspect the optical lens element includes at least a continuous surface and forms a prescription (Rx) zone and a peripheral temporal zone.
Accordingly the spectacle frame is shaped such that the lens element, when mounted, is rotated temporally about a vertical axis through the optical centre thereof.
Alternatively the spectacle frame is shaped such that the lens element, when mounted, is decentred so that the optical axis and direct line of sight remain parallel.
More preferably the spectacle frame is so shaped that the lens element is additionally rotated temporally about a vertical axis through the optical centre thereof.
In a preferred embodiment, the optical lens element includes at least a continuous surface and forming a prescription (Rx) zone and a peripheral temporal zone.
The optical lens element according to this aspect of the present invention may provide prescription (Rx) correction generally in the range of xe2x88x926.0 D to +6.0 D.
In a preferred aspect, the front surface of the optical lens element exhibits a change of base curve across the field of vision of the wearer, the base curves preferably being smoothly blended to avoid a prismatic jump in the Rx zone. In one embodiment, the base curve from the nasal limit to the optical centre may be relatively low, for example from approximately 0.0 D to approximately 6 D. The base curve from the optical centre to the temporal limit may, in contrast, be a high base curve, e.g. of approximately 6.0 D or above, preferably approximately 12.0 D to 18.0 D.
Preferably, the front and/or back surface(s) of the optical lens element include a compound spherical design to provide the desired prescription (Rx) in the prescription zone. More preferably, this prescription zone will extend across the full aperture of the spectacle frames being employed.
It will be understood that an advantage of the present invention is that a common front curve may be utilised across a range of prescription powers. This provides an improvement in the ease of manufacture of optical lens elements, allows a wide range of prescriptions to be fitted to a single frame design and assists in the reduction of inventories.
In a further preferred aspect the optical lens element in the region from the nasal limit to the optical centre may be generally of the meniscus type. Alternatively, the nasal region of the optical lens element may be biconvex in shape. The biconvex shape is preferred, particularly for lenses of high power, due to its ease of mounting and improved cosmetics for the wearer.
In this form the spectacle frame according to the present invention is shaped to receive and retain an optical lens element including a region of reduced or opposite curvature defining a nasal accentuating region such that facial form in the nasal region is accentuated.
The forward reach of the lenses in the nasal region may be utilized at least in part to provide protection of the wearer""s nose from physical impact or radiation damage due to the UV component of sunlight, for example. Lenses having this purpose are desirably curved forward in the nasal region to a horizontal base of 4.0 to 8.0 D so that the combination of lens surface and nose piece of the sunglass frame or unitary lens protects substantially all of the wearer""s nose without intruding on the forward visual field.
More preferably the spectacle frame includes an attached nose-piece, such that the lenses and nose-piece together provide physical or radiation protection to the wearer""s nose.
The peripheral temporal zone of the optical lens element may be at least in part of generally toric shape. The peripheral temporal zone may be at least in part generally piano.
The peripheral temporal zone may itself form an extension of the prescription zone or may be a non-prescription zone.
In an alternative or additional aspect, the peripheral temporal zone may be modified to permit light control within the zone.
It will be understood that the peripheral temporal zone, for a typical sunglass lens element of the wrap-around type, may for example extend for approximately 10 to 25 mm.
In a further aspect of the present invention, the optical lens element may provide prescription (Rx) correction generally in the range xe2x88x926.0 D to +6.0 D
wherein the front surface is capable of being mounted in a frame of constant design curve irrespective of the Rx, such frame curves being 5.0 D and above; and
the back surface provides good clearance from temples or eye lashes; at least one surface exhibits a change of base curve across the field of vision of the wearer.
Preferably the front surface of the lens element has a high compound curve extending from nasal to temporal limits, but the vertical curve is 6.0 D or below.
It will be understood that such vertical curves permit the final prescription lenses, preferably edged lenses, to be adapted to the shape of the wearer""s face and so locate closely in a form of the wrap-around type (a so-called xe2x80x9cgeometrically toricxe2x80x9d design for which the vertical curve of the back surface is selected to maintain the desired through power or Rx correction provided by the lens. This may be distinguished from a conventional xe2x80x9coptically toricxe2x80x9d design wherein one surface is rotationally symmetric and the other is shaped to provide the sphere and cylinder components of the wearer""s Rx without consideration of the facial form of a wearer).
Alternatively the optical lens elements may be adapted for mounting in a spectacle frame of the shield type. Accordingly in a still further aspect of the present invention there is provided a spectacle frame of the shield type, the spectacle frame being shaped to receive and retain a unitary optical lens including
a pair of optical lens elements, each lens element providing prescription (Rx) correction generally in the range xe2x88x926.0 D to +6.0 D
wherein the front surface is capable of being mounted in a frame of constant design curve irrespective of the Rx, such frame curves being 5.0 D and above; and
the back surface provides good clearance from temples or eye lashes; at least one surface exhibits a change of base curve across the field of vision of the wearer.
The optical lens element may, when mounted in a spectacle frame, be rotated temporally about a vertical axis through the optical centre thereof or decentred, or both rotated and decentred.
Such complex surfaces cannot be created by conventional ophthalmic lens processing equipment, but may be generated by current state of the art surfacing equipment such as the xe2x80x9cUltralabxe2x80x9d unit from Micro Optics Inc. This equipment produces a precise surface form by cutting to a computer generated file. The final optical finish may be achieved by applying an overlay coat of optical resin matching the refractive index of the underlying lens. Errors which would be created by polishing the generated surface are thereby avoided or at least substantially reduced.
The front surface of this semi-finished optical lens element has a precise orientation corresponding to the horizontal plane in which tilt and offset may occur. Therefore it may bear other optical features which require precise orientation with respect to vertical and horizontal directions. Examples of these are multifocal power addition for near or intermediate visual distances (both conventional segment type and progressive addition lenses), polarising filters, or cosmetic mirror or tint treatments.
The peripheral temporal zone of the optical lens element according to the present invention may be constructed to maximise cosmetic appearance. Ideally, the peripheral temporal zone should show little or no optical difference from the remainder of the front surface of the ophthalmic lens element. For example, where the prescription Rx surface of the ophthalmic lens is a minus Rx lens, the temporal extension may exhibit a zero refractive power or positive refractive power. The temporal extension may be tapered in cross-section to maximise cosmetic acceptability.
Accordingly, in a preferred aspect the curvature of the front surface is modified in the peripheral temporal zone to substantially correspond to the curvature of the back surface thereof.
It will be understood that the peripheral temporal zone thus formed is a substantially piano extension.
The present invention will now be more fully described with reference to the accompanying figures and examples. It should be understood, however, that the description following is illustrative only and should not be taken in anyway as a restriction on the generality of the invention described above.